As an example of ROIs implemented in a moving picture codec, there are H.263-based encoding and an MPEG-4 object-based encoding. An independent segment decoding (ISD) mode which provides a method of independently decoding a specific region in the H.263 is the same as the MPEG-4 object-based encoding from the point of view that the region that is to—be—independently decoded is treated as one full image in the encoding. However, the ISD mode is different from the MPEG-4 object-based encoding as follows.
1 ISD Mode in H.263
In H.263-based encoding, a method of independently decoding a specific region in an image is provided as an option (see Annex R of H.263). In particular, in the H.263-based encoding, spatial, temporal, and quality scalabilities can be provided by using scalable hierarchical coding.
In the H.263, the quality scalability is provided by using a method corresponding to coarse grain scalability (CGS) of SVC, and the temporal scalability is provided by using a method corresponding to fine grain scalability (FGS) and supporting a variable frame. In addition, in the case of the spatial scalability, similarly to scalable video decoding (SVD), coding is performed in terms of resolutions, and inter-layer coding is performed by using an image having a lower resolution.
2 MPEG-4 Object-Based Coder
In the MPEG-4 object-based coding, an object region having an arbitrary form is coded into a rectangular region defined by a video object plane (VOP). According to this method, similar to the ROI, a specific region in an image is coded in such a way that it can be independently decoded.
The SVC based on the H.264-based encoding has a higher coding rate than H.263 and MPEG-4, and a coding scheme in the SVC is different from those of H.263 and MPEG-4.